1. Field of the Invention
The invention relates to a method for bonding plastic objects together using a hot-melt type of adhesive.
Objects made of all kinds of different materials are attached together by applying adhesives used in the shape of sticks, powders or slabs. All sorts of plastic materials, such as polyamides and polypropylenes, are used as the basis for these hot-melt adhesives. The objects are usually bonded together by applying the hot-melt adhesive in a heated, in other words free-flowing, condition to at least one of the surfaces to be bonded, which is at room temperature, after which the two surfaces to be bonded are pressed against each other. After a short cooling-off period, the two objects are then securely bonded together.
2. Description of Related Art
The process is already known whereby the hot-melt adhesive is first applied to the object, the hot-melt adhesive is then heated above its melting temperature and the two objects are then pressed together. This has been proposed for example for the bonding of floor coverings, in which the hot-melt adhesive is heated up through the floor covering. The floor covering itself was not heated up above its own respective melting temperature, however.
According to a further proposal, installation cases are bonded to the masonry by the process of first heating up the masonry and then attaching the cases by means of a hot-melt adhesive. Also in this case, the masonry""s own melting temperature is not exceeded.
And yet all these methods are unsuitable for some materials, or the ultimate solidity achieved is not sufficient.
The aim of the invention is to establish a method for bonding objects together using a hot-melt type of adhesive that can also be used with materials with which it was hitherto impossible to make use of hot-melt adhesion. This has been achieved by means of heating at least one of the objects to be bonded, in particular multi-layered pipes, in the area in which it is to be bonded to a temperature higher than the melting temperature of the material of which the object is made, in addition to or at the same time as heating and adding a plasticizer-resistant hot-melt type of adhesive.
As experiments carried out have demonstrated, when the method according to the invention is applied, the components of the materials of the objects to be bonded on the one hand and the hot-melt adhesive on the other hand mix together in such a way that an homogeneous and thus also solid bond results. Any plasticizers that may be present, which would otherwise disturb the ability to bond, have no disadvantageous effect when the method according to the invention is applied. Even such materials as polyethylene (PE) can be bonded together using the method according to the invention.
Within the framework of the invention, it is possible to heat up at first at least one of the objects to be attached, in the area where it is to be bonded, until its temperature exceeds the melting temperature of the materials of which the object is made, and subsequently to introduce the hot-melt adhesive.
When materials are bonded that have such different melting points that there is a risk that when the higher melting point is reached, the material with the lower melting point could be destroyed, it is possible first to heat the one object in the area to be bonded so that its melting temperature is exceeded and then to mix it with the hot-melt adhesive flowing in, after which, in a second phase, the hot-melt adhesive that has already been cooled down after being mixed with the material of the first object is re-heated and bonded with the material of the second object.
It is also possible to execute the method according to the invention, however, in such a way that the hot-melt adhesive is heated up to such a temperature and for such a long time that the materials to be bonded melt and flow into the hot-melt adhesive.